While it's not expressly written in the bible one way or another, we can draw conclusions from the text for what most likely took place.

God gives Adam and Eve two commandments. One, don't eat from the tree of the knowledge of good and evil, and two, multiply and replenish the Earth. They were then left alone for a time.

We don't know how long it took for Lucifer to come along, but there doesn't seem to be a whole lot going on between Adam and Eve in the interim They recognize they are meant for each other, and that they are supposed to have children, but the sexual attraction isn't there.

The state of existence they were living in was not what we experience now. In the Garden of Eden, they were not aging, they did become ill, or follow normal bodily cycles. They likely would have continued on indefinitely this way, keeping one commandment—avoiding the forbidden fruit—but not complying with the other—multiplying.

They didn't even realize during this time that they were naked. So, even though they were adults, they were living in a state of innocence or naivete, that didn't go away or change until after eating the fruit.

Post Fall, after being driven out of the Garden of Eden, we read immediately that Adam knew Eve, that she conceived, and they had Cain.

So, while they perhaps had the capacity to have sexual intercourse, they were not inclined to it before eating the fruit, but afterwards, apparently were quick to start keeping the commandment so as to have children.